Basic info: "TOWER" was merely supposed to mean that the arm was subjected to and passed an Ordnance Dept inspection with gauges at the government facility that was a/k/a the "Tower." There was a facility on Bagot St in Birmingham near the gun quarter and of course, the Tower Armoury in London. In reality "TOWER" engraved on the lock plate meant no such thing as the hundreds of thousands of P53s marked that way and imported by the US and CS never got anywhere near a government facility or an inspection with gauges.
A lock plate with no markings other than the date in front of the hammer, especially in italics, would suggest it was made in Belgium. They often have V*R (with a star between the V and the R) under the crown behind the hammer.